Square battery and welding method

Abstract

The present disclosure provides a square battery and a welding method. The square battery includes: a cover plate provided with a pole; and a core provided with a tab, where the tab is directly connected to the pole by laser welding, so that construction of an energy transmission path of the battery is realized, and a charging and discharging function of the core is realized. Additionally, since the tab of the core of the square battery is directly connected to the cover plate of the square battery, an auxiliary welding sheet and a connection sheet are removed, thereby improving the internal space utilization rate and the mass specific energy of the square battery.

What is claimed is: 
     
         1 . A square battery, comprising:
 a cover plate provided with a pole; and   a core provided with a tab, wherein the tab is connected directly to the pole by laser welding.   
     
     
         2 . The square battery of  claim 1 , wherein
 the pole comprises a positive pole and a negative pole;   the tab comprises a positive tab and a negative tab;   the positive tab is directly connected to the positive pole by laser welding; and/or   the negative tab is directly connected to the negative pole by laser welding.   
     
     
         3 . The square battery of  claim 2 , wherein
 the positive tab has a multi-layer positive electrode tab being folded and tightened; the negative tab has a multi-layer negative electrode tab being folded and tightened;   a ratio of a folded size of the multi-layer positive electrode tab to a thickness of the core is less than or equal to 1, and a ratio of a folded size of the multi-layer negative electrode tab to the thickness of the core is less than or equal to 1; and   wherein the folded size of either the multi-layer positive electrode tab or the multi-layer negative electrode tab refers to a clamp positioning size when the tab is folded.   
     
     
         4 . The square battery of  claim 3 , wherein the core has a thickness of 1 mm-700 mm, the multi-layer positive electrode tab has a folded size of 1 mm-500 mm, and the multi-layer negative electrode tab has a folded size of 1 mm-500 mm. 
     
     
         5 . The square battery of  claim 4 , wherein the folded size is ¼- 5/7 of the thickness of the core. 
     
     
         6 . The square battery of  claim 3 , wherein the positive tab is formed by performing ultrasonic pre-welding for the multi-layer positive electrode tab; and/or, the negative tab is formed by performing ultrasonic pre-welding for the multi-layer negative electrode tab. 
     
     
         7 . The square battery of  claim 6 , wherein the ultrasonic pre-welded positive tab is connected to the positive pole by laser final welding; and/or, the ultrasonic pre-welded negative tab is connected to the negative pole by laser final welding. 
     
     
         8 . The square battery of  claim 7 , wherein a ratio of an area for the laser final welding to an area for the ultrasonic pre-welding is less than 1. 
     
     
         9 . The square battery of  claim 7 , wherein a shape for the laser final welding is at least one of an elliptical shape, a circular shape, or a polygon, and a shape for the ultrasonic pre-welding is at least one of the elliptical shape, the circular shape, or the polygon. 
     
     
         10 . The square battery of  claim 6 , wherein a ratio of the area for the ultrasonic pre-welding to the area for the pole is greater than or equal to 0.32 and less than or equal to 0.81. 
     
     
         11 . The square battery of  claim 7 , wherein a ratio of a circumference of a trajectory for the laser final welding to a circumference of a trajectory for the ultrasonic pre-welding is less than 1. 
     
     
         12 . A welding method, comprising:
 performing ultrasonic pre-welding for a tab of a core based on a first solder printing area to form the ultrasonic pre-welded tab, wherein the first solder printing area is determined based on a size and a shape of a pole; and   performing laser welding for the ultrasonic pre-welded tab and the pole based on a second solder printing area to connect the tab with the pole, wherein a ratio of the second solder printing area to the first solder printing area is less than 1.   
     
     
         13 . The welding method of  claim 12 , wherein a shape of the pole is one of a square, a circular shape, or an elliptical shape, and respective sizes of the pole having the shape are respective one or more of a length of a and a width of b, a radius of r, a short half axis of c, and a long half axis of d. 
     
     
         14 . The welding method of  claim 13 , further comprising:
 in response to the shape of the pole being the square, adjusting the length of a based on a first preset adjustment coefficient of λ1 to obtain the adjusted length, wherein 0<λ1<1, adjusting the width of b based on a second preset adjustment coefficient of λ2 to obtain the adjusted width, wherein 0<λ2<1, and determining the first solder printing area based on the adjusted length and the adjusted width;   in response to the shape of the pole being the circular shape, adjusting the radius of r based on a third preset adjustment coefficient of λ3 to obtain the adjusted radius, wherein 0<λ3<1, and determining the first solder printing area based on the adjusted radius; and   in response to the shape of the pole is the elliptical shape, adjusting the short half axis of c based on a fourth preset adjustment coefficient of λ4 to obtain the adjusted short half axis, wherein 0<λ4<1, adjusting the long half axis of d based on a fifth preset adjustment coefficient of λ5 to obtain the adjusted long half axis, wherein 0<λ5<1, and determining the first solder printing area based on the adjusted short half axis and the adjusted long half axis.   
     
     
         15 . The welding method of  claim 14 , wherein 0.7<λ1<0.9, 0.3<λ2<0.5, 0.75<λ3<0.9, 0.85<λ4<0.95, and 0.85<λ5<0.95. 
     
     
         16 . The welding method of  claim 12 , wherein a ratio of the second solder printing area to the first solder printing area is μ, and 0.6<μ<0.8. 
     
     
         17 . The welding method of  claim 12 , further comprising: before the performing of the ultrasonic pre-welding,
 determining a folded size of the tab based on a thickness of the core; and   folding and tightening the tab based on the folding size,   wherein the core has a thickness of 1 mm-700 mm and the folded size is 1 mm-500 mm; or the folded size is less than or equal to the thickness of the core; and   wherein a ratio of the folded size to the thickness of the core is in a range of ⅕ to 1.   
     
     
         18 . The welding method of  claim 17 , wherein a ratio of the folded size to the thickness of the core is in a range of ¼ to 5/7. 
     
     
         19 . The welding method of  claim 12 , wherein the performing of the laser welding for the ultrasonic pre-welded tab and the pole based on the second solder printing area comprises:
 obtaining a preset welding shape for the laser welding;   determining a trajectory for the laser welding based on the second solder printing area and the preset welding shape; and   performing laser welding for the ultrasonic pre-welded tab and the pole based on the trajectory.   
     
     
         20 . The welding method of  claim 12 , wherein a ratio of the first solder printing area to the area for the pole is greater than or equal to 0.32 and less than or equal to 0.81; and/or
 a ratio of a circumference of a trajectory corresponding to the laser welding to a circumference of a trajectory corresponding to the ultrasonic pre-welding is less than 1.